The effect of the chemical hepatocarcinogen 2-acetylaminofluorene (2-FAA) and its non-carcinogenic analogues on proliferation and differentiation of fetal and adult hepatocytes using well-defined in vitro cultures systems will be studied. The major emphasis of studies in chemical carcinogenesis is to determine how cancer cells develop from apparently normal cells. Short and long-term primary and continuous in vitro cultures of fetal and adult rat hepatocytes will be characterized. Cell growth and protein production will be maintained and the effects of 2-FAA and its analogues on these parameters determined. Alpha-fetoprotein (AFP) and albumin production will be used as a potential marker for effects of the carcinogen since in vivo experiments suggest that one of the earliest actions of hepatocarcinogenesis is to induce the formation of AFP. Since AFP is also a marker for cell growth, careful control studies will be done to determine the role of cell proliferation and carcinogen exposure in regard to control of AFP and albumin production. In addition, the ability of hepatocyte cultures to metabolize the carcinogen will be examined and the effect of modifying agents, such as hormones, will be determined. Because a number of variables can be studied in vitro that are not able to be controlled in vivo, these studies may provide insights into the mechanism of action of an hepatocarcinogen.